Abstract In a pulse tube cryocooler, the gas in the pulse tube can be thought of as an insulating piston, transmitting pressure and velocity from the cold heat exchanger to the hot end of the pulse tube. Unfortunately, convective heat transfer can carry heat from the hot end to the cold end and reduce the net cooling power. Here, we discuss one driver of such convection: steady acoustic streaming as generated by interactions between the boundary and the oscillating pressure, velocity, and temperature. Using a perturbation method, we have derived an analytical expression for the streaming in a tapered pulse tube with axially varying mean temperature in the acoustic boundary layer limit. Our calculations showed that the streaming depends strongly on the taper angle, the ratio of velocity and pressure amplitudes, and the phase between the velocity and pressure, but it depends only weakly on the mean temperature profile and is independent of the overall oscillatory amplitude. With the appropriate tapering of the tube, streaming can be eliminated for a particular operating condition. Experimentally, we have demonstrated that an orifice pulse tube cryocooler with the calculated zero-streaming taper has more cooling power than one with either a cylindrical tube or a tapered pulse tube with twice the optimum taper angle.
Suppression of Acoustic Streaming in Tapered Pulse Tubes
Cryocoolers 10 ; 307-313
2002-01-01
7 pages
Article/Chapter (Book)
Electronic Resource
English
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